1. Field of the Invention
This invention relates to building foundation form work including a spacer useful in form work, and a method of constructing and using form work for building foundations.
The problem to which this invention is directed is the present cost of providing a foundation for a building which will be sufficiently strong to resist substantially expansive soils.
2. Description of the Prior Art
It has been conventional to cut trenches into the ground and then subsequently pour concrete into these, and in some cases providing above ground form work so that concrete can be poured above ground level as well as below.
Such work in cutting the trenches and laying up the form work is extremely labour intensive but furthermore, substantially constrains the style of foundation that is most appropriate for a particular application.
In other words, on many occasions, especially where soil is known to be soft or expansive over different seasons, it would perhaps be better to have an integral slab on which the building would sit, but hitherto the cost of this would be equivalently so high as to make it in many cases impractical.
It has been previously known to propose form work and also to include rectilinear elements within a foundation form work so that concrete is then poured over these so that they are subsequently incorporated into the foundation.
Once again, the problem has been the cost of providing such elements which have been previously proposed as being constructed of polystyrene foam.
More recently a cardboard box has been proposed which has considerably reduced the potential cost of this part but there has been a major problem in respect of holding such cardboard boxes in relation one to the other in such a way that the boxes will retain with sufficient integrity their relative position especially during the pouring of concrete, and secondly such that any means that might be used to hold the boxes in a relative position do not of themselves unreasonably reduce the integrity of any foundation that is subsequently poured.
The problem in particular arises because of the inherent constructional characteristics of a cardboard box and the extremely high forces that result when concrete is being poured in a channel on one side of a box where there is no equivalent material on the opposite side of the box.
It has also to be remembered that such side pressure will be aggravated by vibration conventionally used by concrete pourers to ensure removal of voids within the foundation being poured.